200 



P.J. Webber et al. 



Graminoids (16) 

 5: 



LO molstur* HI /.CTtoluble phosphate/// 



Forbs (33) 



id moisture 7/7 Z.<7soluble phosphoti/// 



Shrubs (6) 



LO moisture HI /.^soluble phosphate/// 



Lichens (29) 



LO moisture HI ^(7toluble phosphate/// 



Bryophytes (22) 



LO moisture HI /.Soluble phosphate/// 



Total 



LO moisture HI /.CTsoluble phosphate/// 



FIGURE 6-7. The number of species per 10-m^ plot of the most common 

 growth forms and the total number of species within the principal axes of 

 the ordination. The total number of species of each growth form is given 

 in parentheses. (After Webber 1978.) 



FUNCTIONAL RELATIONSHIPS OF GROWTH FORMS 

 AND ENVIRONMENTAL GRADIENTS 



Functional Definition of Growth Forms 



The growth forms defined on the basis of morphological habit differ 

 in functional characteristics related to the environmental gradients. 

 Functional characteristics include leaf longevity, timing of leaf growth, 

 location of the perennating bud, location of stored organic and inorganic 

 nutrients, leaf resistance to water loss, photosynthetic rates, carbon and 

 nutrient costs of constructing new leaf material, and location of absorb- 

 ing roots. 



The graminoid forms are characterized by sequential leaf produc- 

 tion and, for single graminoids, a rapid leaf turnover (Tieszen and 

 Wieland 1975, Johnson and Tieszen 1976). The leaf longevity may be 

 shorter than the growing season. This pattern results in a high annual 

 growth respiration cost, and is generally associated with relatively high 



